/*
 * Copyright 2002-2012 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.jdbc.support.nativejdbc;

import org.springframework.util.ReflectionUtils;

import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.sql.*;

/**
 * Implementation of the {@link NativeJdbcExtractor} interface for the
 * Jakarta Commons DBCP connection pool, version 1.1 or higher.
 *
 * <p>Returns the underlying native Connection, Statement, etc to application
 * code instead of DBCP's wrapper implementations. The returned JDBC classes
 * can then safely be cast, e.g. to {@code oracle.jdbc.OracleConnection}.
 *
 * <p>This NativeJdbcExtractor can be set just to <i>allow</i> working with a
 * Commons DBCP DataSource: If a given object is not a Commons DBCP wrapper,
 * it will be returned as-is.
 *
 * <p>Note that this version of CommonsDbcpNativeJdbcExtractor will work
 * against the original Commons DBCP in {@code org.apache.commons.dbcp}
 * as well as against Tomcat 5.5's relocated Commons DBCP version in the
 * {@code org.apache.tomcat.dbcp.dbcp} package.
 *
 * @author Juergen Hoeller
 * @since 25.08.2003
 */
public class CommonsDbcpNativeJdbcExtractor extends NativeJdbcExtractorAdapter {

    private static final String GET_INNERMOST_DELEGATE_METHOD_NAME = "getInnermostDelegate";


    /**
     * Extracts the innermost delegate from the given Commons DBCP object.
     * Falls back to the given object if no underlying object found.
     *
     * @param obj the Commons DBCP Connection/Statement/ResultSet
     * @return the underlying native Connection/Statement/ResultSet
     */
    private static Object getInnermostDelegate(Object obj) throws SQLException {
        if (obj == null) {
            return null;
        }
        try {
            Class classToAnalyze = obj.getClass();
            while (!Modifier.isPublic(classToAnalyze.getModifiers())) {
                classToAnalyze = classToAnalyze.getSuperclass();
                if (classToAnalyze == null) {
                    // No public provider class found -> fall back to given object.
                    return obj;
                }
            }
            Method getInnermostDelegate = classToAnalyze.getMethod(GET_INNERMOST_DELEGATE_METHOD_NAME, (Class[]) null);
            Object delegate = ReflectionUtils.invokeJdbcMethod(getInnermostDelegate, obj);
            return (delegate != null ? delegate : obj);
        } catch (NoSuchMethodException ex) {
            return obj;
        } catch (SecurityException ex) {
            throw new IllegalStateException("Commons DBCP getInnermostDelegate method is not accessible: " + ex);
        }
    }


    @Override
    protected Connection doGetNativeConnection(Connection con) throws SQLException {
        return (Connection) getInnermostDelegate(con);
    }

    @Override
    public Statement getNativeStatement(Statement stmt) throws SQLException {
        return (Statement) getInnermostDelegate(stmt);
    }

    @Override
    public PreparedStatement getNativePreparedStatement(PreparedStatement ps) throws SQLException {
        return (PreparedStatement) getNativeStatement(ps);
    }

    @Override
    public CallableStatement getNativeCallableStatement(CallableStatement cs) throws SQLException {
        return (CallableStatement) getNativeStatement(cs);
    }

    @Override
    public ResultSet getNativeResultSet(ResultSet rs) throws SQLException {
        return (ResultSet) getInnermostDelegate(rs);
    }

}
